1. Field of the Invention
This invention relates to new solutions or dispersions of cationically and optionally non-ionically hydrophilically modified polyisocyanate addition products with built-in acyl urea groups, a process for their preparation and their use as coating compounds for flexible or rigid substrates or as sizes for paper.
2. Description of the Prior Art
Processes for the preparation of ionically modified polyurethanes are known and have been described, for example, in the following literature: DE-PS No. 880,485, DE-AS No. 1,044,404, U.S. Pat. No. 3,036,998, DE-PS No. 1,178,586, DE-PS No. 1,184,946, DE-AS No. 1,237,306, DE-AS No. 1,495,745, DE-OS No. 1,595,602, DE-OS No. 1,770,068, DE-OS NO. 2,019,324, DE-OS No. 2,035,732, DE-OS No. 2,446,440, DE-OS No. 2,345,256, DE-OS No. 2,345,245, DE-OS No. 2,427,274, U.S. Pat. No. 3,479,310 and Angewandte Chemie 82, 53 (1970) and Angew. Makromol. Chem. 26, 85 et seq. (1972).
The aqueous dispersions of the above mentioned polyurethanes may be used for a wide range of purposes, e.g. as adhesives or for coating various flexible or non-flexible substrates.
In spite of the large number of known processes and the products obtained from them, however, the demand persists for aqueous dispersions which have quite specific properties.
The process described below provides the possibility of a simple method of altering the properties of the products in the desired direction over a wide range by suitable choice of an organic substituent attached by way of acyl urea group.
The preparation of isocyanate polyaddition products containing acyl urea groups is known per se and has been described, for example, in DE-OS No. 2,436,740 and DE-OS No. 2,714,293. In these known processes, the products are either prepared in the form of solutions and converted into films to form coatings, lacquer coverings or foils (DE-OS No. 2,436,740) or the polyhydroxyl compounds containing acyl urea groups are first prepared and then converted into foams containing acyl urea groups, (DE-OS No. 2,714,293). It was not foreseeable, however, that this principle would also be applicable to the chemistry of aqueous polyurethane dispersions and in particular that the dispersions according to the invention described below of polyurethanes containing hydrophobic side chains attached by way of acyl urea groups would be at least equal in quality as paper sizes, for example to the high quality products disclosed in DE-OS No. 2,400,490. In particular, the dispersions and solutions of polyurethanes containing cationic groups and hydrophobic side chains described below are superior to the paper sizes disclosed in the last mentioned prior publication due to their improved sizing action both in alum-free paper and in alum-containing or pre-sized paper or paper containing wood.